Ferrous base chromium-nickel-titanium alloy



June 9, 1953 G. MOHLlNG. ET AL FERROUS BASE CHROMIUM-NICKEL-TITANIUM ALLOY Filed July 19, 1951 HOURS TO RUPTURE 5 Sheets-Sheet l OUR ALLOY HEAT NO. 4329? EFFECT OF SOLUTION TEMPERATURE ON STANDARD AND V-NOTCH RUPTURE STRENGTH AND RUPTURE DUOTILITY TESTS AT I200F. 60,000 F281.

STANDARD RuPTuRs-7/ eo 100 l u: D 500 I E D I 400 .005" R. V-NOTGl-l RUPTURE Z v\ M Q 20:: l0 '3 9 loo 5 g I I c 0 I600 I100 I800 I900 2000 2100 SOLUTION TEMPERATURE F.

HEAT TREATMENT:

SOLUTION TEMP. l HR. OIL I325E l6 HOURS AIR 4 F lg. I

INVENTORS Gunther Moh/ing Was/l n. Dyrkacz June 9, 1953 G. MOHLING ET AL Filed July 19. 1951 EFFECT F TITANIUM CONTENT ON v-NoTcH RUPTURE STRENGTH AND RUPTURE DUCTILITY [STANDARD TEST] TEsTs A l200F.-60,000 R31.

ALLOY FERROUS BASE CHROMIUM-NICKEL-TITANIUM ALLOY 5 Sheets-Sheet 2 A VS. OUR ALLOY OUR ALLOY RUPTURE V-NOTCH RUPTURE TEST HOURS [ALLOY A HEAT oo 2.40 2.80 a.

TITANIUM CONTENT TREATMENT I800F. HR. OIL

l325 F. l6 HRS. AIR

Fig. 2

N 0 9 ELONGATION STANDARD RUPTURE TEST INVENTORS" Gunther Moll/fag Was/l M Dyrkacz QMJmMAJQMV THE II? AT TOR/VE Y8 June 9, 1953 G. MOHLING ETAL 2,641,540

FERROUS BASE CHROMIUM-NICKEL-TITANIUM ALLOY Filed July 19, 1951 5 Sheets Sheet s ouR ALLOY V-NOTOH AN-D STANDARD RUPTURE STRENGTH v s, BRINELL HARDNESS TESTS AT I200E-60,000 P.8J.

so o

v- NOTCl-l RuP'ruRa ace hr 400 l o v I 300 a STANDARD uPTuRE I00 BRINELL HARDNESS Fig. 3

INVENTORS Gunther Mohling Wasil W. Dyrlraa 4%, 711A W, M

THEIR ATTORNEYS June 9, 1953 G. MOHLING ET AL 2,641,540

FERROUS BASE CHROMIUM-NICKEL-TITANIUM ALLOY 5 Sheets-Sheet 4 Filed July 19, 1951 OUR ALLOY Heat Treatment l650F-l hr., Oil Quenched plus Heat 43297 l325 F- IG hrs.,Air Cooled A.$.T.M. Grain Size Range 8 to finer than 8- Average: Finer than 8 arm ALLOY Heat Treatment 0 m 4329 I800 F lfxfusoll Quenched l32 5F-l6 hrs., Air Cooled Fig. 5

INVENTORS A.$.T.M. Grain Size Gun/fer Mal/fling Wasi W. Dyr 00: Range 5 to finer than 8 BY am/fif ZZZ MV Average 6 to finer than 8 THE/I? ATTORNEYS June 9, 1953 G. MOHLING ET AL 2,641,540

FERROUS BASE CHROMIUM-NICKEL-TITANIUM ALLOY Filed July 19, 1951 s Sheets-Sheet 5 OUR ALLOY Heat Treatment Hem 43297 I900 F IP21; O|l Quenched I325 F- l6 hrs., Air Cooled A.S.T.M. Grain Size Range 2 to 8 Average 3 to 6 OUR ALLOY Heat Treatment 20 0F-lhr. O'l ched Heat 4329? 5 Fig. 7

a V I A.S.T.M Grain Size mmvroxs Gunther Mohling Range Larger than I to 6 BY w /l n, Dyrkacz Average Larger than I to 3 emlfic wm THE/R ATTORNEYS 1325' F- 16 hrs., Air Cooled Patented June 9, 1953 f UNITED STATES PVYATENJTW o FF1ca* FERRQUS BASE 'CHROMIUM-NICKEL- TI ANI AL Y Gunther Mohling, 'Loudonville, and 'Wa'sil 'W'. Dyrkacz, Newtonville, N. Y., assignors to Allee gheny Ludlum Steel Corporation, Bracken? ridge, Pa., a corporation of, Pennsylvania Application July 19, 1951, stamin 237,534

8 Claims. (01. 755-1281) This invention pertains to ferrous alloys and particularly, to improved austenitic chromiumnickehtitanium ferrous alloys.

Dueto recent strides bein made in the development of aircraft engines, e. g. jet engines and gas turbines, the need has arisen for new and improved alloys'which may be made commercially' on a production basis and which will stand up whenhighly stressed rotating parts are to operate .at a temperature of around 1000 to 1350 F. Heretofore, there has been no heat treatable .alloy which would fully meet requirements' in this respect as to ductility within such atemperature range and which could be produced on a production basis by ordinary arc melting, high tonnage procedure. An alloy of this type for use-in rotating parts must not only stand up at such temperatures, but must have other characteristics which will comply with the rather rigid and high requirements of such a utilization.

Heretofore, one, typeof alloy has been'produoed which We will hereinafter specify as alloy A that falls within theminimum requirements of such, a utilization, except for ductility at the critical .(norma1 embrittlement) temperature of 1000 to 12 F. to which rotating parts are subjected, Alloy A is thus limited to stationary utilizations' as it has an insufficient ductility for rotating parts. Alloy A has the following general composition: small amounts of carbon, silicon, manganese and a1uminum,.about 30 %1nickel, 15% chromium and 2.0% titanium. This .alloy is a commercial type, but has an extremely short rotating part operating life period, is notch sensitive,and fails suddenly.

Another alloy which will be hereinafter designated as alloy B '(see U. S. Patent No. 2,519,406) has been found to generally fulfill the minimum requirements of the subject utilization up 'to and including operation of the working parts at such temperature, but has only been successfully'produoed on a pilot plant scale and at a relatively high cost. This latter alloy requires special forging and heat treatment processing and is produced by induction melting. The closely controlled hot-cold forging work ties up forging equipment for long periods of time. We, as 'well as those skilled in the art, have definitely determined that such anallo y cannot beproduced on a large commercial scale by conventional 2 steel "making processes and have the requisite properties.

It thus appears that there is a definite and critical need for an'improved heat treatable alloy which can be produced in high tonnage and which will have a generally higher ductility at operating'temperatures than those now available and which will retain its ductility in the temperature range of 1000-1200 F. (normal brittle range) and well up to 1350 F. Such temperatures-are encountered in ordinary usage of rotating engine parts and thus, the life of such parts is governed by the ductility of the metal. Furthermore, explosion failure which is caused by verybrittle characteristics, must be avoided at all costs and if failure is to occur, it must be of a gradual nature, so that steps may be taken to replace the part before its utilization becomes dangerous.

It has thus been an object of our invention to provide an improved chromium-nickel-titanium. ferrous alloy of an austenitic type which will not only have good forgeability, machinability and an excellent high strength, but will retainits ductilityin a moving partutilization and especially, at elevated temperaturesof 1000 to 1200 F.;

.Another object has been to provide a wrought, austenitic, precipitationehardened alloy which will meet requirements for rotating aircraft engine parts;

A further object has been to provide an alloy of this type which can be produced on a commercial production basis and can be simply and In carrying out our invention, we have been:-

able to provide an alloy which has highly superior characteristics under all conditions of utilization, which can be produced by conventional melting practice, whose properties can be dee op d. by ea eatm t ith ut spe al worke 3 ing and heat treating procedures, and which can be produced relatively inexpensively and processed simply to develop its characteristics. It has a life period far in excess of 1000 hours in rotating engine part utilizations, as based on test data comparisons. It can be hot worked and treated in commercial size heats using standard or conventional equipment. In this alloy, the maximum carbon content is highly critical, and the manganese content provides increased rupture ductility and improved forgeability. Also, vanadium is a highly important and critical element. The alloy permits a higher manganese, to silicon ratio. The manganese and vanadium are employed as alloy additions and not as scavengers, as they are introduced directly into the melt and not at the end for cleanup purposes and thus, are essentially in solid solution form in the alloy. The proportioning of vanadium to titanium and molybdenum contents is also highly critical and is believed to constitute the crux of the invention from the standpoint of the specified ranges of chromium, nickel and silicon contents.

v In this alloy, although not necessary, cobalt can be added up to 25% to further increase its strength. The element aluminum is generally considered to contribute toward brittleness. We have found that it increases rupture ductility considerably, but at the expense of rupture strength (as evidenced by melt A-4l6 of Table .VI). In our alloy, we have discovered that the adverse effect of a higher aluminum content on rupture strength can be more than ofiset by the addition of cobalt in amounts up to 25%, e. g. as shown in Table VI, melt A-409 (which contains 1.2% aluminum) is considerably strengthened by the addition of cobalt. The fact that our alloy can take a higher percentage of aluminum is further indicative of its novel char acteristics.

Our alloy in its broader aspects contains carbon in relatively low amounts up to .15% maximum, manganese within a range of .50 to 3.00% (not as a scavenger but as an essential alloying element introduced into the solution), silicon up to 1.50%, chromium within a range of about 5 to 22%, nickel within a range of '7 to 50%, titanium within a range of .50 to 3.50%, a relatively low percentage of molybdenum of about .25 to 2.00%, a highly critical percentage of vanadium of .10 to 1.50%, up to 25% cobalt, and up to 2.5% aluminum. In our alloy, the remainder is iron with incidental impurities, such as nitrogen, phosphorus and sulphur. While in general, increasing the titanium content increases the rupture strength and tensile strength, it also decreases rupture ductility below a useful level when a critical titanium content is reached. In alloy A, this content appearsto be about 1.5% titanium, and in alloy B, about 1.9% titanium. In alloys of our invention, useful ductility is maintained up to at least about 3% titanium (see Table IV). This is obtained by proportioning of the other elements and particularly, of the vanadium and molybdenum to offset or reduce the embrittling efiect of titanium within the ranges specified. Our alloys, thereforapermit a much higher than ordinaryrange'of titanium, while still insuring high strength combined with good rupture ductility.

- The optimum range of our alloy which we have found highly satisfactory consists of carbon in an amount up to .15 maximum, about .5 to'2.0% manganese, about .4 to 1.5% silicon, about '12 to 18% chromium, about 20 to 35% nickel, about 1.0 to 1.5% molybdenum, about .10 to .50% vanadium, and about 1.5 to 2.9% titanium, with aluminum in a maximum amount of 0.35%.

A specific alloy which we have produced with optimum results contains about .08 maximum carbon, about 1.0 to 2.0% manganese, about .50 to 1.25% silicon, about 12 to 16% chromium, about 24 to 28% nickel, about 1.0 to 1.5% molybdenum, about .10 to .50% vanadium, about 1..'75 to 2.25% titanium, and incidental amountsof aluminum from the addition of ferro-alloys.

It will be noted that our alloys save on highly strategic materials and as will hereinafter be shown by test data, are inherently ductile,.even at temperatures of about 1200 F., as demonstrated by notched rupture tests. Grain coarsening begins at about 1850 F., see Figures 4 to 7, inclusive. Further, our alloys do not need cold working, since their properties can be developed by a solution treatment and age-hardening (see Figure 5) and they can be handled in melting,

forging, and heat treating in the same manner as any commercial alloy.

Best results are obtained by employing a solution heat treatment of about 1800 F. for one hour and rapidly cooling in a suitable fluid quenching medium (such as oil, air or water), followed by age hardening at about 1325 F. for about 16 hours plus air or furnace cooling (in a gaseous atmosphere). That is, it has been determined that l800 to 1850 F. is about the highest practical temperature to which the alloy can be raised before grain coarsening sets in and temperatures higher than this, as shown by Table II, produce some gain of strength at the cost of rupture ductility and increased notch sensitivity. Another advantage of our alloys is that a high titanium content can be employed without seriously adversely effecting their ductility, see Table IV. Ductility may be increased by lowering the amount of titanium, but with a reatly reduced rupture strength and tensile strength below about 1.45% titanium. We have found that vanadium ment, optimum results are obtained by the 1800 F. solution treatment and subsequent age hardening treatment which has been previously discussed.

As compared to the best alloy available prior to our present invention, namely alloy B (as produced by special precedure), a typical alloy of our invention has a Brinell hardness of to 170 in the solution treated condition, as compared to hardness of 140 to for alloyB, and as solu tion treated and aged,'has an assured hardness of 248 to 341 and higher, as compared to hardness of 248 to 302 for alloy B.- It appears that our alloys not only have an increased hardness, strength, etc., but have an increased ductility such that the operating life of working parts can be greatly improved and particularly so, when in operation, they are subjected to heat of up to about 1350 F. and particularly, in the critical range of 1000 to 1200 F. In addition, products made with our alloys can be produced at much lower cost than alloy B, as they do not require special forging and heat treating practice. Center segregation is reduced or eliminated in our alloys when-produced in large commercial melts so as to provide material which will have sufiicient center ductility in large forgings, such as'liurbirie rotors. In our alloys, segregation is minimized by limiting the molybdenum content to a 2% maximum.

The V-notch rupture tests as employed herein are an indication of rupture ductility. When-high temperature metals of the type herein being 'conan included angle;-ct;fi? with a .005 inch radius at the base of the n tch. A I I V In the following Table I. we have set forth test data-on alloys or our'ifiventiofibn'three commer cial, productionheats-0152 and-10 --tons madeiningot sizes one" to square, 1 1

(Standard) c- Room Tern erature Tensile: Yie (1 Strength...

. Tensile Strength.

Percent Elongation. Percent Reduction 1193mm neat ssoo Heat 62918 sidered have a low rupture-ductility, the V-notch Table II and the photomicrographs of Figures rupture life is considerably less than the standard 41) 4 to '7, inclusive, illustrate the importance of rupture life and thus, they are considered to be notch sensitive. In carrying out this test, we

"vf-notch rupture strength, rupture grain size solution heat treatment in developing the structure and properties of our alloys.

ductility and ANALYSIS HeatNo. Y o. Mn s1 Or Ni Mo Ti v A1 s'rREss ltUPTURE AT 1,200 F.--60,000 p. s. 1.

make a men or .040 m deep 1111 a. .275 men diameter test bar and the sides or the ndtdh form jTable iirsets rortirs xtymca melts lcyi' iv'ing" test data esto thesam.

TA L 111 j 1 Stress Hrs to Percent Percent "M211: p. s. i. Rupture Elong. Red.Area

Std 00,000 101 5.9 1110 A485 n ooog 32 s s 16 Melt No 0 Mn 81 Cr Ni Mo Tl y 2.1

tivity. This is true even when hardness is in excess of 290 Brinell which is in contradiction to alloy B. In this connection, attention is called to the data set forth in Table IV and Figure 3.

TABLE IV Ejfect of increasing Ti content on tensile,

hardness and rupture properties Melt No Ti 0 Mn 81 Cr N 1 Mo V Al 1. 7 04 1. 14 78 14. 9 26. 5 1. 3 34 16 1. 9 05 1. 28 76 14. 8 26. 3 l. 3 35 14 2. 5 04 1. 14 1. 02 15. O 26. 5 1. 3 38 1O 2. 9 05 1. 28 1. 11 14. 7 26. 4 1. 3 39 12 RUPTURE PROPERTIES Rock 0 Hrs. to Percent Melt Type Test F. Stress Rup- :33 Red. gg

ture Area g A 105 10. 0 17. 5 31 I 14-374,; L 538 32 v 82 15. 3 33. 0 211 10. 6 22. 2 32 A-373 902 112 17. 3 41. 0 32 A371 225 15. O 22. 0 36 288 11. 6 19. 5 41 A-372. 354 39 118 11. 2 46. 5

R0 OM'TEMPE RATURE PRQPE RTIES 02% Tensile Percent Per cent Brinell gg i Strength Elong. Red. Area Hardness Solution treated at 1,800 F. and aged at 1,325" F.

titanium content up to 3% may be "effected with- 5 out impairing its rupture ductility, while at the same time increasing room temperature hardness and tensile strength. It will be noted that we can obtain higher yield and tensile strengths (by the use of our permissible higher range of titanium) without adversely affecting rupture ductility due to the controlled vanadium additions. That is, our controlled vanadium additions. permit the use of a higher titanium con- Although; both the manganese and the vanadium contribute individually to good rupture ductility, they tend to decrease strength. A too high amount of manganese would decrease rupture strength greatly. However, the controlled amount of molybdenum increases the rupture strength. Thus, we add somewhat small amounts of vanadium, keep the manganese at about 1.0 to 2.0% (1.5% optimum) and the molybdenum at about 1.0 to 1.5% (1.25% optimum) to obtain both good tent without seriously increasing notch sensi rupture'strength and ductility. In this connec {Table V, wherein melts In Figure 1, we have. graphically shown the effect .of the temperature of solution treatment of our alloy, based on standard and V-notch rupture strength and rupture ductility test data taken at 1200 F. and using 60,000 p. s. i.

In Figure 2 of the drawings, we have shown graphically the effect of titanium content on TABLE V Stress-Rupture at 1,2o0 Fr 60.000 p. s. i.

Melt C MD. Si C1 Ni Ti MD. I A1 7 Q I 1 Hrs. to Percent ggg ptu 3 .05. 1.3 .73; 14.2 25.2; 1.8 .32 -29 22. (5.0 9.0 15 5.7 v10.4 .04' 1.3 .82 14.4 26.1 1.8 .03 =92 8.8- 16.0 .05 1.3 .76 14.8. 26.3 1.9 .14 211- 10.41 22.2 .04 1.14. .78 14.9 26.5 1.7. .16 105 10.0 17.5 1 :56."; .05 2.1- .59 14.4 25.3 1.8 .31 19. '7.8i 18.0 14-57.... .04 4.9V .54 142 25.4. 1.6. .50 4 13. 5. 15.2

High aluminum content has a similar effect as manganese in that .it increases rupture ductility at the expense of rupture strength, even in the presence of molybdenum. This can be counteracted and the rupture strength greatly increased by the addition of cobalt as shown in Table VI.

TABLE v1 V-notch rupture strength and rupture ductility, based on a. comparison of our alloy with alloy A. This graph illustrates the improvement of rupture ductility and V-notch rupture strength of ou all y s compared with alloy vA whentested at the critical embrittling temperature.

Efiect .of aluminum and cobalt Stress-Rupture at 1,200 Fl-60,000 p. s. 'i. I

Melt O Mn Si Cr"Ni"li M0 V Al C0 i 5 TypeTest, Hrs. to 1 Percent i s- V Rupture E1 Area 11-4160 O4 1. 16 63 14. 7 26. O l. 8 1. 3 27 3. 1 Std. l3 5 30. 7 66.5 11-409..." 04 1.11 85 14. 8 26. 1 1. 7 a 1. 2 32 1. 1 20. 1 std 491 3. 6 '15. 7 A409 V-notclL 681 y It will be noted that the V-notch test of melt A409 shows a life of 681 hours which indicates that cobalt added (within the specified range) to our alloy does not make itjnotch sensitive.

Furthermore, the strengthening effect of cobalt in increasing the rupture strength is even more pronounced in our alloys when the titanium content approaches 3%, as is illustrated in Table VII.

TABLE VII Efiect of cobalt Melt G M1; Si or Ni ri Mm v; n .00

StressRupture nt1,200 .StressrRupture at 31,350 F.-60,000 -p. s. -i. F.-.42,500 p..s. i.

Melt t r v Erato Percent ggg Hrs. to Percent g g Rupture Elong. A163: Rupture Elong. Area" 4142A" 301: 7..5 11.0 3183 16:3 28.3 A-A2 1+ 6 -9.

{lest progress.

.Table'IV. As compared to the patent disclosure of alloy B, where his said that notch rupture strength is much lower than regular rupture strength once the hardness goes above about 290 Brinell, this graph shows that the Va-notch rupture strength of our alloy is higher than the regular rupture strength allthe way up to :341 Brinel-l. A comparison of the curves of Figures 2' and 3 and Table IV discloses that our alloy has a rupture elongationof about 10% at a-hardness of 341 Brinell, as contrasted to 5% of alloy 13 at the same .Brinell.

Inour melts, commercial scavengers and deoxidizers, such as calcium-silicon-manganese, calcium-silicon, silicon-zirconium, Grainal (titanium-aluminum-vanadium) Lan Car Amp about 50% lanthanum, 30% cerium and 20% rare earth metals) and L-Metal (about the same composition as Lan Ger Amp), have been used with advantage.

An alloy of our invention is particularly characterized by its ability to develop high strength properties (in its heat-treated state') up to 1350 F. with an inherently good rupture ductility and notch rupture strength. That is; the alloying elements of an alloy of our invention are so proportioned as to give it a high rupture ductility and strength at operating temperatures up to -1350 F. and a good ductility within the normally brittle range of 1000 to 1200 F. Such alloy is of an austenitic, ferrous-metal-containing type, such that the remainder is iron or substantially all iron with incidental impurities. "For example, production melts may contain impurities such as sulphur, phosphorus, selenium, nitrogen, copper,

zirconium, cerium, and lanthanum.

What we claim is:

1. A commercially producible and forgeable austenitic alloy steel suitable for moving part usage and having an inherently good rupture ductility with a high notch rupture strength at elevated temperatures of about 1000 to 1300 F., in which manganese, chromium, nickel,titanium, molybdenum and vanadium are the only essential elements, are critical within the ranges specified, and the specified contents of the elements manganese and vanadium are essentially in solid solution form in the alloy, and in which aluminum may be present in incidental amounts and up to about 2.50% with the presence of cobalt of up to about,25%; the composition consisting of carbon in a relatively small amount up to a maximum of about .15%, about .50 to 3.00% manganese, up to about 1.50% silicon, about to 22% chromium, about 7 to 50% nickel, about .50 to 3.50% titanium, about .25 to 2.00% molybdenum, about .10 to 1.50 vanadium, and the remainder iron with incidental impurities.

2. An improved alloy-as defined in claim 1, as

. further characterized by its fully developed properties when solution treated for about one hour at and quenched-from about 1800 R, followed by age hardening for about 16 hours at and quenched from about 1325 F.

3. A commercially producible and forgeable austenitic alloy steel suitable for moving part usage and having an inherently good rupture ductility with a high notch rupture strength at elevated temperatures of about 1000 to 1300 F., in which manganese, chromium, nickel, titanium,

V molybdenum and'vanadium are the only essential elements and the specified contents of the elements manganese and vanadium are essentially in solid solution form and in which aluminum may be present in incidental amounts from the addition of ferro-alloys; and the composition consisting of carbon in a relatively small amount up to a maximum of about .15%,.about .50 to 3.00% manganese, up to about 1.50% silicon, about 5 to 22% chromium, about '7 to 50% nickel, about .50 to 3.50% titanium, about .25 to 2.00% I molybdenum, about .10 to 1.50% vanadium, and

the remainder iron with incidental impurities.

4. A commercially producible and iorgeable austenitic alloy steel suitable for moving part usage and having an inherently. good rupture ductility with a high notch rupture strength at elevated temperatures of about 1000 to 1300 F., in which manganese, chromium, nickel, titanium, molybdenum and vanadium are the only essential elements and the specified contents of the elements manganese and vanadium are essentially in solid solution form, and in which aluminum --may be present up to about .40%; the composition consisting of carbon in a relatively small amount up to amaximum of about .15%, about 150 to 3.00% manganese, up to about;1.50% si1i,;

con, about 5to 22% nickel, about 1.50 to 3.50% titanium; about .50 to chromium, about 7 m 50% 1.50% molybdenum, about .10 to 1.50% vanadium,

and the remainder iron with incidental impurimolybdenum. and vanadium are the only essential elements and the specified contents of the elements manganese and vanadium are essentially in solid solution form, and in which aluminum may be present in a maximum amount of about 110%; the-composition consisting of carbon in a relatively small amount up to a maximum of about .15 about .50 to 2.00 manganese, about .40 to 1.50% silicon, about 12 to 18% chromium,

about 20 to 35% nickel, about 1.50 to 2.90% titanium, about 1 to 1.50% molybdenum, about .10 to .50% vanadium, and the remainder iron with incidental impurities.

6. A commercially producible and forgeable austenitic alloy steel suitable for moving part usage and having an inherently good rupture ductility with a high notch rupture strength at elevated temperatures-of about 1000' to 1300 F..,

in which manganese, chromium, nickel, titanium, molybdenum and vanadium are the only essential elements and the specified contents of the elements manganese and vanadium are essentially in solid solution form, and in which aluminum may be present in incidental amounts from the addition of ferro-alloys; the composition consisting of carbon in a relatively small amount up to a maximum of about .08%, about 1 to 2% manganese, about .50 to 1.25% silicon, about 12 to 16% chromium, about 24 to 28% nickel, about 1.75 to 2.25% titanium, about 1 to 1.50% molybdenum, about .10 to .50% vanadium, and the remainder iron with incidental impurities.

7. A commercially producible and forgeable austenitic alloy steel suitable for moving part usage and having an inherently good rupture ductility with a high notch rupture strength at elevated temperatures of about 1000 to 1300 F., in which manganese, chromium, nickel, titanium, molybdenum and vanadium are the only essential elements and the specified contents of theelements manganese and vanadium are essentially in solid solution form, and in. which aluminum may be presented up to about .35% the composition consisting of carbon in a relatively small amount up to a maximum of about .08%, about 1 to 2% manganese, .50 to 1.25% silicon, about 12 to 16% chromium, about 24 to 28% nickel, about 1.75 to 2.25% titanium, about 1 to 1.50% molybdenum, about .10 to .50% vanadium and the remainder iron with incidental impurities.

maximum of about 06%, about 1 to 2% manganese, about .70 to 1.50% silicon, about 13 to 15% chromium, about 24 to 27% 'nickel,'about 1.90 to UNITED STATES PATENTS Name Date Harrington June 9, 1936 Number m Name Date Pilling July 21, 1936 Franks Dec. 16 1947 o Franks Dec. 16, 1947 FOREIGN PATENTS Country -Date France Jan. 6, 1948 

1. A COMMERCIALLY PRODUCIBLE AND FORGEABLE AUSTENITIC ALLOY STEEL SUITABLE FOR MOVING PART USAGE AND HAVING AN INHERENTLY GOOD RUPTURE DUCTILITY WITH A HIGH NOTCH RUPTURE STRENGTH AT ELEVATED TEMPERATURES OF ABOUT 1000 TO 1300* F., IN WHICH MANGANESE, CHROMIUM, NICKEL, TITANIUM, MOLYBEDENUM AND VANADIUM ARE THE ONLY ESSENTIAL ELEMENTS, ARE CRITICAL WITHIN THE RANGES SPECIFIED, AND THE SPECIFIED CONTENTS OF THE ELEMENTS MANGANESE AND VANADIUM ARE ESSENTIALLY IN SOLID SOLUTION FORM IN THE ALLOY, AND IN WHICH ALUMINUM MAY BE PRESENT IN INCIDENTAL AMOUNTS AND UP TO ABOUT 2.50% WITH THE PRESENCE OF COBALT OF UP TO ABOUT 25%; THE COMPOSITION CONSISTING OF CARBON IN A RELATIVELY SMALL AMOUNT UP TO A MAXIMUM OF ABOUT .15%, ABOUT .50 TO 3.00% MANGANESE, UP TO ABOUT 1.50% SILICON, ABOUT 5 TO 22% CHROMIUM, ABOUT 7 TO 50% NICKEL, ABOUT .50 TO 3.50% TITANIUM, ABOUT .25 TO 2.00% MOLYBDENUM, ABOUT .10 TO 1.50% VANADIUM, AND THE RAMAINDER IRON WITH INCIDENTAL IMPURITIES. 